Detection Method Of Oil Quality Paraments Based On Quartz Tuning Fork Sensor

During the process of oil using,if the performance parameters of the oil can be know in time,such as the viscosity,density,dielectric constant of the oil,then the deterioration degree of the oil can be determine in time,and then a more accurate judgment on the timing of oil replacement can be make.Among these paraments,the viscosity,density and dielectric constant of oil are important indicators to judge the quality of oil.The laboratory measurement method of them has high precision but cannot measure in real time for its large volume.Therefore,it is an urgent need for the development of automotive intelligence to design an online sensor that can detect the quality parameters of oil in real time.In this paper,the detection method of oil quality parameters with quartz tuning fork resonator as the sensitive element was studied deeply,and the detection system was developed.Based on the analysis of piezoelectric characteristics and electromechanical coupling model of quartz tuning fork,the principle and method of measuring oil viscosity and density with quartz tuning fork were given,and the decoupling measurement of oil viscosity and density was realized.On this basis,a theoretical method to improve the accuracy of viscosity measurement and expand the range of viscosity measurement,namely,the classification method of high and low viscosity measurement,was put forward.According to this method,the viscosity coefficient and density coefficient of the quartz tuning fork sensor are calibrated in the range of 0-120c P viscosity and 0.83-0.88 g/cm~3 density.Based on the equivalent circuit of quartz tuning fork,further studied of the shunt capacitance in the equivalent circuit and a tuning fork relative dielectric constant of the dielectric theory relations between the two arms,and then deduced the oil dielectric constant and the quartz tuning fork resonator theory formula of the relation between the shunt capacitance,and presented a tuning fork were calculated based on admittance circle and susceptance shunt capacitance of the two methods,had carried on the comparative analysis to it.On this basis,the theoretical method of measuring the dielectric constant of oil by using quartz tuning fork was given,and the dielectric constant coefficient was calibrated in the relative dielectric range of 1.8-2.8.In this paper,a system software for measuring oil viscosity,density and dielectric constant simultaneously based on quartz tuning fork was developed,which includes a single chip computer program and an oil quality parameter calculation program.On this basis,the experimental study of the detection system was carried out.The comparative experimental study resulted with the most advanced FPS sensor of MEAS Company in the world at present prove that:The viscosity measurement range was more than doubled to 0-120c P,and the viscosity accuracy in the 0-120c P range was 2.98%.Within the density measurement range of 0.83-0.88g/cm~3,the average error of density measurement is 0.5171%.The average measurement error of the relative permittivity within the measurement range of 2.1-2.3 is 0.267%.